Mail sorting machine



Jan. 7,-1969' H. J. ROSENBERG ETAL 3,420,368

I MAIL SORTING MACHINE Filed Sept. 14, 1966 Sheet of 4 FIG, 2

J Fi .3

m /N VfN ro/es "B3 Harold J. Easenberg,

W/ John P. Surrells,

|]}- 54 Joseph 15'. 771 121 L48 I 5 azi Jan. 7, 1969 H.IJ. ROSENBERG ETAL 3,420,368

MAIL SORTING MACHINE Filed Sept. 14 1966 m m m H I vm N5 QM M .2935 ozQwaew Fm All. mW mm mu wx' f vQ Nmm Nm Mm mm Sheet Jan. 7, 1969 H. 'J. ROSENBERG E L MAIL SORTING MACHINE Filed Sept. 14. 1966 lllll a I l a? l| QM B I km W NM on T Q M. 4 mm United States Patent P 3,420,368 MAIL SORTING MACHINE Harold J. Rosenberg, John R. Sorrells, and Joseph E.

Trent, Washington, D.C., assignors to B. H. Bunn Company, Chicago, Ill., a corporation of Illinois Filed Sept. 14, 1966, Ser. No. 579,238 US. Cl. 209-73 9 Claims Int. Cl. B07c 3/10 ABSTRACT OF THE DISCLOSURE This invention relates to apparatus for automatically sorting mail, data cards, and the like, in accordance with variously coded information imprinted, punched, or otherwise associated with the material to be sorted.

It is very common for certain businesses, such as insurance companies, banks, magazine publishers, etc., to solicit business, conduct surveys, or the like, by mail and, for the convenience of the addressee, to enclose a reply envelope in the material sent to the addressee. The replies so received usually must be segregated as to the mailing to which they relate, or as to the geographical area from which the replies emanate, as well as other differentiating criteria. Where the mailing is extensive, the sorting of the reply mail is not only time-consuming, but requires services of large numbers of clerks who may have to be of a temporary character and hence difficult to obtain. In some of the mailings, the reply envelopes are imprinted with a visual code in the form of dots, dashes, or bars, arranged in a predetermined pattern by which the sorter can differentiate one envelope from another.

Efforts have been made in the past in related arts to sort mail according to address by electronically reading the printed or type address on envelopes. Other efforts have been made to sort checks in accordance with a magnetically imprinted numerical code. Such efforts have resulted in complex, expensive equipment which only the larger institutions can afford to purchase or lease.

The principal object of this invention is the provision of a relatively inexpensive and simple apparatus for sorting stacked envelopes in accordance with coded information imprinted or otherwise formed on the envelopes.

As a more specific object, this invention has within its purview the provision of a sorting machine which automatically removes envelopes from a stack, one at a time, transports the envelopes past a reading head, and deposits the envelopes into a selected one of a group of pockets or bins according to instructions from the reading head.

Envelopes which are to be sorted one at a time must move in a stream past a series of gates, one of which will be opened in accordance with the code imprinted on that envelope. Those gates which are farthest removed from the origin of the stream of envelopes require a length of time to reach such removed gate which may be greater than the time interval between envelopes passing the reading head. This then requires a memory device in the sorter which stores information received from the reading head after said reading head was cleared to read the coded information on a succeeding envelope. Such memory devices, or information storage devices, as heretofore proposed, have been complex and expensive, and it is accordingly a further object of this invention to provide a means 3,420,368 Patented Jan. 7, 1969 in a mail sorter for simply and economically storing information from a reading head and subsequently releasing the stored information by the movement of the envelope from which information was originally obtained by the reading head.

A further object of this invention is the provision of a mail sorting device wherein the mail sorts are divided into groups or modules according to the distance of the groups from a reading head, the distant groups being provided with power flip-flops which are triggered by means controlled by the position of the envelope being sorted.

These and other objects of this invention will become apparent from the following detailed description when taken together with the accompanying drawings in which FIG. 1 is a schematic plan view of the mail sorter of this invention;

FIG. 2 is a side elevation, partly in section, of the mail sorter of FIG. 1;

FIG. 3 is a greatly enlarged view of the face of an envelope with a portion broken away, showing the preferred code bit format used in the sorting machine of FIG. 1;

FIGS. 4 to 7 are greatly enlarged fragmentary plan views of the means on the mail sorter for automatically removing one envelope at a time from a stack of envelopes and feeding the removed envelope int-o the first feed rollers of the sorter;

FIG. 8 is a schematic wiring diagram of the means for controlling and Operating the sort gates for the sorter; and

FIG. 9 is a schematic wiring diagram of a modification of means of FIG. 8.

Considering first the mechanical aspects of the sorter, there is provided in the embodiment chosen to illustrate this invention an appropriate table-like frame 10 on which is an upper surface 11 disposed at a sufficient elevation from the floor to make all parts thereof conveniently accessible to an operator without requiring him to stoop. At the left hand end, as viewed in FIGS. '1 and 2, of the upper surface 11, and disposed substantially cent-rally thereon, is a vertical plate 12 which preferably has a rectangular configuration of a size greater than the largest envelope to be sorted by the machine. Said plate acts as an abutment for a stock of envelopes 13, which all have been faced the same way and which rest upon one longitudinal edge thereof. Said stack 13 is compressed against vertical plate 12 by a pressure plate 14 held against the stack by a spring 15 reacting against an abutment 16 on surface 11. If desirable, spring 15 and abutment 16 may be located below surface 11 and made to contact plate 13 by a Suitable extension on said plate (not shown).

On the opposite side of vertical plate 12 from stack 13 is disposed a pick-off mechanism which is shown more clearly in FIGS. 4 to 7, inclusive. Said figures are views of the device as seen by an operator standing at the loading side (upper) of the sorter and show the vertical plate 12 and the stack of envelopes 13. The pressure of spring 15 is relatively light, so that a minimal friction force is developed between adjacent envelopes to interpose a minimum resistance to the sliding of one envelope upon another.

The pick-off mechanism is comprised of a shaft 17 extending vertically through the upper surface 11 of the frame 10 and continuously driven through appropriate gearing 18 (FIG. 2) from a shaft 19 disposed horizontally in frame 10 and providing the drive for all of the drive rollers in the sorter. A motor 20 and chain 21 also disposed within frame 10, serve as a source of power for shaft 19. On shaft 17 is loosely mounted a roller 22 which is provided with a protrusion 23 extending radially therefrom around approximately 20% or 72 of the circumference of the roller. Said protrusion 23 is preferably cylindrical in contour and forms the letter-contacting surface of the roller. The material of which the protrusion 23 is made is preferably of a friction character such as rubber, cork, or the like.

Protrusion 23 is adapted to extend through a window 24 in plate 12 where it can contact and frictionally engage the face of an envelope 25 adjacent to plate 12. A suitable drive for roller 22 is provided by a radial abutment 26 on shaft 17 which is adapted to contact a pin 27 extending axially of roller 22 into the path of movement of abutment 26. A torsion spring 28 having one end (not shown) secured to shaft 17 and the other end 29 continuously bearing against pin 27, normally urges pin 27 against the abutment 26. Thus abutment 26 and pin 27 provide a lost motion connection between drive shaft 17 and the roller 22.

An adjustable friction finger 30 is provided to hold back the envelope adjacent to envelope 25, should said adjacent envelope exhibit a tendency to move with envelope 25. Friction finger 30 may be manipulated by a knob 31 (FIGS. 7 and 1) within easy reach of the operator.

Adjacent pick-off rollers 22 is the first pair of feed rollers 32 and 33. These feed rollers, as shown in FIGS. and 6, are disposed in line with envelope 25 as it leaves the protrusion 23, and are also located close enough to pick-off roller 22 so that both the feed rollers and the pick-off roller engage envelope 25 at the same time. The diameter and speed of the feed rollers 32, 33 are such as to move envelope 25 with a linear velocity of 120 inches per second. This velocity is higher than the peripheral velocity of protrusion 23, for the reason that it is desirable to accelerate envelope 25 in two stages rather than at once. This means, therefore, that once the envelope is gripped between rollers 32 and 33 it moves faster than the peripheral velocity of protrusion 23 as the latter is driven by shaft 17. Because of the lost motion connection provided by protuberance 26 and pin 27, the protrusion 23 may be momentarily driven at some higher speed dictated by the movement of envelope 25 until said envelope is clear of the protuberance 23,

Rollers 32 and 33 are driven from shaft 19 through suitable gearing 34. Substantially identical gearing is used to drive a series of feed or transport rollers shown at 35, 36 and 37, the last mentioned being repeated at the entrance to each pair of sorts.

For a better understanding of the remainder of the apparatus, a description of the envelope and the code format used thereon will now be given. Referring to FIG. 3 it may be noted that the envelope may have imprinted on the face thereof a series of vertically disposed and aligned dashes which have been designated B1, B2, B3 and B4. These dashes individually are code bits, and for purposes of illustration are shown as black rectangles which may be printed on the envelope approximately one-half inch from the right hand edge thereof, as viewed in FIG. 3. Other code formats may be used with this invention, such as dots or discrete magnetic substances, or in the case of post cards, perforations of various configurations. Greater or lesser numbers of code bits may also be employed, depending upon the number of sorts to be made. In the illustrative example given in FIG. 3, four code bits are used which theoretically provides 16 unique combinations and therefore 16 different sorts. In the apparatus chosen to illustrate this invention, however, only 12 sorts are shown, it being understood that four sorts can be added to the 12 to take full advantage of the possibilities presented by the four bits.

Thus, in FIG. 1 the 12 sorts S1 to S12 are shown as being symmetrically arranged around a central straight line which is representative of the path followed by a letter through the sorting section of the apparatus. Each sort, such as S1, is provided with a pair of transport rollers 37 to propel a letter thereinto or past the sort, as the case may be, the path taken by the letter being determined by a mechanical pivoted gate 38.

Each sort, such as S1, is comprised of a chute defined by substantially vertical walls 39, 40 and a horizontal floor 41 which terminates in a pocket or bin 42 into which the envelopes fall and in which they are stacked flat. Said pockets 42 have transparent doors 43 which may be hinged as shown at 44 in FIG. 2. The transparent door permits the operator to observe the fullness of a pocket and alerts him to the necessity of removing the envelopes already in that pocket.

If, perchance, an envelope which is not coded should be included in the stack, or if there should be an error in the coding so that the apparatus does not direct the envelope into any of the sorts S1S12, said envelope may then be deposited at the end of the apparatus in the area 45 which may comprise a slightly downwardly inclined surface having a wall 46 across the end thereof to prevent complete ejection of the envelope out of the apparatus.

Between feed rollers 32 and 36 is disposed a reading head 47 adapted to direct a beam of light upon each of the code bits B1 to B4 and, by reflected light from the code bit area, influence individual photo cells disposed in the head, there being one photo cell for each code bit area beam.

It is essential, inasmuch as the code bits are differentiated in a vertical direction, that the envelope be presented to the reading head with its lower edge 48 resting squarely on surface 11 as a reference plane. For various reasons, however, the envelopes may not leave the rollers 32, 33 in this position and, accordingly, means are provided intermediate rollers 32, 33 and the reading head for settling each envelope upon surface 11. This means is comprised of relatively closely spaced vertical walls 49, 50 between which an envelope, such as 51, is loosely confined. Said walls 49, 50 converge slightly toward rollers 35 so that envelope 51 is directed into the area from which rollers 35 may readily and unfailingly seize the envelope.

Rollers 32, 33 on the one hand and 35 on the other are spaced apart a distance considerably greater than the length of an envelope 51. Furthermore, rollers 32, 33 are so inclined as to cause the envelope 51 to be ejected therefrom in free flight so that when the envelope falls upon surface 11, it is automatically properl oriented with respect to surface 11 and therefore with respect to the reading head 47. The free flight of the envelope 51 is illustrated in FIG. 2. From the time envelope 51 enters rollers 35 until it is directed to its ultimate destination, it is always in contact with a set of feed or transport rollers such as 36 or 37. Its speed is thus precisely determined as well as its location relative to a succeeding envelope.

Reading head 47 which is also sometimes referred to herein as a scanning head, has not only the four photoelectric cells influenced by the reflected light from the four code bits areas, but has a fifth photo cell which is used to detect the leading edge of an envelope as it passes by, and upon detecting such leading edge, actuate the circuitry for the sorter in a manner to be hereinafter described. Depending upon the combination of code bits on any given envelope, one (and only one) of the sorting gates 38 will be actuated by a solenoid controlled by the circuitry.

Referring now to FIG. 8, there is shown in this figure a block diagram of the electronics or circuitry for the sorting device of FIGS. 1 and 2. As stated previously, the configuration shown in the diagram is based on the use of a four bit code and the illustrated 12 output sorts. The edge detector photo cell in the reading head 47 is sensitive to a beam of light disposed in the path of movement of the envelope at the reading head 47 and is shown schematically as a line 52 in FIG. 1. Another photo cell is associated with a second edge detector shown as a line 53 in FIG. 1, located at the end of the third set of rollers 37 and before the fourth set, so that as the envelope passes the second edge detector 53 it can actuate other circuitry which controls the operation of the sort gates 38 associated with the sorts S7 to S12.

Thus in FIG. 8 the code bit photo cells are designated by the reference characters 54, 55, 56 and 57, and are shown schematically as circles. The photo cell for the first edge detector is shown at 58 and the photo cell for the second edge detector is shown at '59. The output signal from each photo cell is fed to individual amplifiers 60-64, which amplify these signals to a level suitable for logic operations. From the amplifiers 60-63 the code bit signal is sent to the set gate of individual bit tip-flops, said flip-flops being designated by the reference characters 66, 67, 68 and 69.

The signal from the amplifier 64 for the edge detector cell is sent to a one-shot multivibrator 70, the assertion output of which is connected through a lead 71 to the set gates of each of the flip-flops 66 to 69 and the negation output of which is coupled through a capacitance 73 and a lead 74 to the reset gates of the flip-flops 66 to 69.

The one-shot multivibrator 70, when tirggered by a signal from the edge detector cell 58 as amplified by amplifier 64 switches to the on state and stays on for a fixed time of approximately five milli-seconds. The assertion output in the lead 71 is negative during the oil state and goes positive during the on state. The negation output in lead 74 is positive during the off state and goes negative during the on state. The assertion signal, being fed to the reset gate of all four flip-flops, serves to clear or reset the flip-flops before the code on the envelope enters the scan area of the reading head 47.

The lead 71 is connected directly to the set gate of all four flip-flops and serves as a sampling pulse for the four code cell amplifiers. The code amplifiers are sampled for the full one-shot duration of five milli-seconds. During this time, the letter moves approximately one-half inch and the code passes through the View Of the code photo cells 54 to 57, inclusive. Any code cell which sees a bit B1 to B4, generates an output signal which is amplified and fed to the set gate of its respective flip-flop 66 to 69, and causes such flip-flop to be set. If a cell does not see a code hit, its flip-flop is left in the cleared state. At the end of the five milli-second sampling period, the set gates of the flip-flops are inhibited, and any further signals from the code cells due to other printing on the envelope is ignored.

The ultimate objective of the sorter is to cause the sort gate 38 for the particular sort S1 to S12 to be actuated to direct letters having the same code to the same pocket 42. As shown in FIG. 8, in one typical example, the gate 38 is shown as pivoted about a vertical axis and actuated through a link 75 by the armature 76 of a solenoid 77.

Each solenoid 77 is operated by a solenoid driver shown schematically as a rectangle in FIG. 8, and the several solenoids are numbered 79 to 90 for solenoids S1 to S12, respectively. Each solenoid driver is connected to the output of an and gate 91 which serves as a code detector and responds to only one of the sixteen possible code patterns. Said and gates 91 are thus connected to the outputs of the bit flip-flops 66 to 69 in unique ways so that, for example, the and gate 91 for driver 79 is connected to the assertion output B1 of flip-flop 66 and the negation outputs of the bit flip-flops 67, 68 and 69. The solenoids driver 83 may have its and gate con nected to the assertion output B1 of flip-flop 66, the negation output B2 of flip-fiop 67, the assertion output B3 of flip-lop 68, and the negation output B4 of flip-flop 69. Thus solenoid driver 79 will be turned on only when the letter code contains bit B1 and not bits B2, B3 and B4. Solenoid driver 80 may be energized only when the letter code contains B2 and not bits B1, B3 and B4, etc.

For an illustrative example of the operation of the sorter of this invention, let it be assumed that a letter which contained bits B1 and B3 in its code has passed reading head 47. This letter then causes flip-flops 66 and 68 to be set and flip-flops 67 and 69 to be left in the cleared condition. This is a code combination for driver 83, and accordingly it will be energized to actuate solenoid 77 and turn sorter gate 38 to deflect a letter into the sort S5. This gate remains actuated until the leading edge of the next letter is detected by edge detector cell 58, at which time the reset gate of each of the flip-flops 66 to 69 receives a signal which clears all of the flip-flops for the next code, that is, for the code of the oncoming letter. Any letter which is sorted into one of the first six pockets S1 to S6 is processed in a similar manner, the only variance being the code configuration and resultant gate actuation.

The division of the sorts into two or more groups or modules is dictated by the fact that the feed roller 22 and reading head 47 can process a letter in less time than it takes the letter to travel from the reading head to the last pair of sorts S11, S12. Therefore, to take maximum advantage of the more rapid operation of the feed roller and reading head, it is necessary to split the gates into groups requiring a travel time for the envelope which is just a little less than the time for an envelope to be picked up by the feed roller 22 and read by the reading head 47. The second or third groups, as the case may be, require logic operation which involves the retention of the signals from the reading head 47 after the reading head has been cleared by the edge detector of the next envelope to appear before the head.

To illustrate the need for a division of the sorts into groups, let it 'be assumed that a second letter is fed from the input stack 13 which contains bits B2 and B4 as its code. The letter is detected, as before, by edge detector cell 58 and this code is sensed and stored in the bit flipfiops 66 to 69, inclusive. In the example assumed, flipflops 6-6 and 69 would be on and flip-flops 66 and 68 would be off. As shown in FIG. 8, this is the code for sort gate S10 and it therefore does not energize any of the first six gates S1 to S6. This lettter then travels along a straight path until it reache the second edge detector 53, or as shown in FIG. 8, edge detector cell 59. Said cell 59 is mounted in the example given approximately 28 inches downstream from edge detector cell 58 and senses the leading edge of the letter immediately after it passes the sixth sort gate. The signal from the second edge detector photocell 59 is amplified by amplifier and fed into a squaring circuit 92 which provides two complementary output signals B92 and B92. These two signals are used to control solenoid drivers 85 through 91), which are different from solenoid drivers 79 to 84. The latter are essentially power amplifiers which are gated on and off, whereas drivers 85 to are wired as power flip-flops which can be set and reset in the usual manner. When output signals are present at B92 and B92, these indicate that a letter has passed the first six gates and is approaching the second set of six gates. The output leads B92 and B9? are connected through capacitors 93 and 94 to the reset and and gates 95 and 96, respectively, of the solenoid drivers 85 to 90, respectively. At this time BE clears the drivers 85 to 90 inclusive of any previous setting, and a pulse from B92 is fed to the set gate 96 of each of the drivers. If the letter code stored in the bit flip-flops 66 to 69 satisfies the set gate of one of the solenoid drivers 85 to 90, then that driver is turned on and remains on until another letter is detected by edge detector 59. In the example chosen to illustrate the operation of the device, driver 88 would be set and the letter would be sorted into pocket S10.

The fact that solenoid drivers 85 to 90 inclusive function as flip-flops, is very important in determining the letter thru-put rate of the sorter. If drivers 85 to 90 did not have storage capabilities, the maximum thru-put rate would be determined by the physical distance from the scanning head 47 to the last sort gate 53 for sort S12, and by the linear velocity of the letter. In the machine chosen to illustrate this invention, the distance from the scanning head 47 to the last gate 53 is 50 inches and the letter velocity is 120 inches per second. At this velocity, approximately 415 milli-seconds elapse between the time that a letter code is read and the time that the leading edge of the letter reaches the last sort gate. If storage were not provided at the second six drivers 85 to 90, the minimum interval between letters would be 415 milliseconds, and if letters were presented to the scanning head at less than this minimum interval, missorts would result.

By providing storage capability in the second six drivers 85 to 90 and triggering said second six drivers with the second edge detector 59, the effective thru-put rate of the sorter is doubled. The minimum letter interval is now determined by the letter velocity and the distance from the scanning head 47 to the second edge detector photo cell 53. In the illustrative embodiment this distance is 28 inches, and at a letter velocity of 120 inches per second, is equivalent to a time interval of 232 milliseconds. This means that letters can be presented to the scanning head 47 at intervals which are slightly greater than 232 milliseconds without chance of missorts. The intervals must be slightly greater, since the second edge detector 53 must be given an opportunity to function before the reset gates of the bit flip-flops 66 to 69 are triggered by the next envelope. In other words, within 232 milliseconds from the time its code is read, any given letter has either been sorted into one of the first six pockets, or its letter code has been transferred from the bit flip-flops 66 to 69 to the solenoid driver flip-flops 85 to 90 which operate the second six sort gates S7 to S12. In either case, the bit flip-flops can be cleared and a new code entered without affecting the previous letter.

The principle of dividing a plurality of sorts into modules made up of groups of sorts in order to increase, or at least to maintain, a predetermined thru-put rate can be extended almost indefinitely. An arrangement involving three modules, as an example, is shown in FIG. 9. In that figure, a code format using five code bits is used, which theoretically will yield thirty-two unique combinations and therefore thirty-two possible sorts. For simplicity only eighteen sorts are shown in FIG. 9, said eighteen sorts being divided into three modules (M1, M2, and M3) of six sorts each. Module M1 has sorts l to 6, M2 has sorts 7 to 12, and M3 has sorts 13 to 18.

At the reading head, which may be located at the same position in the sorter as head 47, five photocells 97-101 are used to pick up the five code bits which may be identical in form to those shown in FIG. 8. The pulses from photocells 97-101 are fed to individual amplifiers 102-106 and the amplified pulses are then connected to the set gates of a first bank of flip-flops 107-111, said flip-flops having been first reset and then sampled by the one-shot pulse of a first edge detector designated generally by reference character 112. If the letter code read is for one of the six sorts in the first module M1, then the appropriate solenoid driver 113-118 and the sort gate operated thereby will be actuated to deflect the letter into the proper bin before it reaches the second edge detector.

If the letter code is for a sort in the second module M2, no sort gate is actuated until the letter reaches a second edge detector designated generally by reference character 119. This second edge detector may be identical to the first edge detector and is located physically between the sixth and seventh sort gates. The function of the second edge detector 119 is to transfer the bit code from the first bank of flip-flops 107111 to a second bank of flip-flops 120-124. This is accomplished, as before, by the pulse from a one-shot multivibrator included in the edgedetector circuit, which first resets fiip-fiop 120424 and then sets the bit code into said flip-flops. As soon as the code appears in the second bank of flip-flops 120124, the appropriate driver 126-131 and the sort gate operated thereby will be actuated to deflect the letter into its bin before the letter reaches the third edge detector photocell.

If the letter code is for a sort in the third module M3,

no gate is actuated until the letter reaches a third edge detector designated generally by the reference character 132. The third edge detector is similar in all respects to the first two edge detectors and is located physically between the twelfth and thirteenth sort gates. At this time, the pulse from the said third detector one-shot multivibrator transfers the bit code from the second bank of fiip-fiops 124 to appropriate driver flip-flops 133- 138 in the third module M3 which actuate the proper sort gate and deflects the letter into its intended bin.

It may be apparent that additional modules of sorts may be used, with the bit code transferred from one module to the next by edge detectors working in conjunction with banks of bit flip-flops, without in any way decreasing the thru-put rate of the letters. As in the two-module system of FIG. 8, the rate at which letters are sorted, i.e., fed to the first edge detector, is determined by a combniation of the letter linear velocity and the length of one module, not by the overall distance between the first edge detector and the last sort gate in the machine.

It may be appreciated that the division of the sort gates into modules is dictated by the travel time of a letter from the pick-off station to the reading head, and by the desire to avoid the use of a plurality of individual reading heads stationed along the path of the letter, or alternatively to avoid the use of complex and expensive memory devices in which to store the code bit information after the reading head has been reset by the next letter. The use of :banks of flip-flops intermediate the first and last module, and the use of driver fiip-fiops in the last module, provides a means for storing code bit information in, and cascading it from, module to module without requiring a duplication of reading heads and without resorting to expensive memory devices.

It is understood that the photoelectric bit scanning devices and edge detectors, the amplifiers, flip-flops, and gates and power flip-flops referred to hereinabove, are selected from readily available devices and hence are not described in detail.

We claim:

1. The combination in a device for sorting coded articles in accordance with a bit code associated with each said article of an article pick-off station, a plurality of sort gates, each sort gate being adapted to pass articles having a unique bit code, means for moving an article from the pick-off station to the sort gates, means intermediate the pick-off station and sort gates for reading the bit code on each article, a reference supporting surface at the reading means, and means for operating the sort gates in accordance with the bit code read by said reading means, characterized in that the means for moving an article from the pick-off station comprises means for imparting free flight to said article prior to its reaching the reading means, said free flight terminating on said reference supporting surface, whereby to assure correct referencing of the bit code relative to said reading head.

2. The combination according to claim 1, further characterized in that said articles are rectangular and relatively flat, said pick-off station comprises a vertical abutment, resilient means for holding said articles with the fiat side thereof against said abutment, a window in said abutment, rotatable means adapted to project through said window to contact and propel the article adjacent thereto horizontally, said means for imparting free flight to said article comprising a pair of rollers inclined to the verical to direct the article upward and horizontally, and spaced vertical walls between which the article is guided in its free flight.

3. The combination according to claim 1, characterized further by bins associated with each sort gate, and transport rollers adjacent the upstream side of each sort gate and adapted to propel an article along sort gate and into the 'bin associated therewith.

4. The combination according to claim 1, characterized further in that said sort gates are arranged in pairs disposed one on each side of the path of said article, and said pairs are arranged substantially equi-distantly along said path of said article.

5. The combination according to claim 4, characterized further in that said pairs are divided into modules, said means for moving an article from the pick-off station comprising transport rollers in each module adapted to move an article therethrough, and means for synchronizing-the operation of the pick-01f station with said rollers whereby to cause the maximum time of an article to move through a module to be less than the time interval between successive articles moving through the pick-off station.

6. The combination according to claim 4, characterized further in that said sort gates are divided into adjacent modules along the path of said articles, means at the entrance to each module for detecting the presence of an article threat, means associated with each module for storing code bit information obtained by the reading head, and means controlled by said article detecting means for transferring the information from one storing means to the adjacent downstream storing means.

7. The combination according to claim 6, characterized further in that said storing means comprises flip-flops adapted to be set in accordance wtih said code bit information.

8. The combination in accordance with claim 6, characterized further by solenoids for operating said sort gates, solenoid drivers for said solenoids, and means controlled by said flip-flops for controlling operation of said solenoid drivers, the drivers for the solenoids in the last module in the path of the articles comprising power flip-flops.

9. The combination in accordance with claim 1, characterized in that said articles are rectangular letter envelopes, and the bit code format comprises a series of vertically spaced bars disposed a predetermined distance from the leading vertical edge of said envelope.

References Cited UNITED STATES PATENTS 2,971,414 2/1961 Owen 209-74 3,037,625 6/1962 Azari 209--72 3,141,540 7/1964 Burkhardt 20972 X M. HENSON WOOD, JR., Primary Examiner. R. A. SOHACHER, Assistant Examiner.

US. Cl. X.R. 27136 

